Field of the Invention
The present invention relates to wireless communications, and more specifically, a method and apparatus for receiving data.
Related Art
Intensive research is underway in LTE (Long Term Evolution) release 12 for enhanced performance in light of capacity, coverage, coordination between cells, and costs. Under discussion is, from a technical perspective, adoption of various techniques including small cell enhancement, macro cell enhancement, new carrier type, and machine type communication for performance enhancements in LTE release 12.
Enhancements in capacity and transmission coverage, which LTE release 12 is targeting, may be achieved by small cell enhancement based on inter-site carrier aggregation, LTE-WLAN (Wireless Local Area Network) integration, and macro cell enhancement. Assuming the situation that the cell size is decreasing, the UE's movement is frequent, and the traffic signaled as the UE moves may increase. To address such issues, a method being discussed in LTE release 12 is to optimize small cells by reducing signaling that is made from RANs (Radio Access Network) to the core network based on small cell enhancement.
Further, the NCT (New Carrier Type) discussed in LTE release 12 is a newly defined frame type, different from the legacy frame configuration. The NCT may be a carrier type optimized for small cells, but this may also apply to macro cells. For example, the NCT may reduce overhead that is caused upon transmitting reference signals, such as CRSs (cell-specific reference signals), and may demodulate downlink control channels based on DM-RSs (demodulation reference signals). Newly defining the NCT may save the energy of base stations and reduce interference between HetNets (Heterogeneous Networks). Further, use of the NCT may decrease reference signal overhead that arises upon transmission of data through a plurality of downlink antennas. In the NCT, specifically, the legacy frame structure (for example, CP length, subframe structure, duplexing mode) is maintained, but the control channel and/or reference signal may be newly defined.